fix(overton): correct SVD axis interpretation, drop pass rate, synthesis rewrite
- SVD axis 2 sign corrected: negative = nationalist (PVV -0.56, FVD -0.36), positive = kosmopolitisch (Volt +0.27). Centrists moved LEFT on both axes while right-wing moved further right culturally (+0.146 gap). 'Acceptance without conversion' named as unifying interpretation.
- U1: Figure 1 merged to single panel, pass rate removed, 5 centrist_support lines
- U2: Pass rate columns dropped from all breakpoint tables, PR narrative cut
- U3: Findings report rewritten: SVD section replaced, synthesis restructured into 3 tiers, extremity LLM bias qualified
- U4: Axis labels and sign convention added to svd_stability_report.md
- Added centrist_support_mp column (MP-weighted, correlates 0.998 with party-level)
